Corn has been the traditional cereal for the preparation of tortillas in Mexico and some countries of Central America. Also, corn tortillas, corn chips, and tortilla chips have widely penetrated the market of the United States and some countries of Asia and Europe. In Mexico, approximately 70% of the total corn production is consumed in the form of tortillas. For low resource population, tortillas are the main source of calories and proteins.
The traditional method to process corn into tortillas (nixtamalization) goes back to early Mesoamerican civilizations, and the basic steps of the process have remained basically unaltered since. The traditional process, whole corn is cooked in a boiling water-lime (or water-ash) solution for a short time (5-45 min) and steeped in this solution, as it cooks, for a period from 12 to 18 hours. The cooking liquor, called nejayote, is discarded; with it is lost the fraction of the pericarp and germ dissolved in the nejayote. The cooked, steeped, and drained corn grains (nixtamal) are washed to remove excess lime; here again, a part of pericarp and germ material is lost . The total corn fraction lost varies from 7 to 15%. The nixtamal is ground with a pestle and stone into masa. Finally, the masa is flattened into thin disks that are cooked on a hot griddle for 30-60 seconds on each side to produce tortillas. Tortillas prepared by the traditional method just described generally show excellent Theological characteristics, such as puffing and elastic strength.
On the other hand, some of the main problems associated with the method of the previous art are:
1. Part of the pericarp and germ is discarded, loosing important amounts of thiamin, riboflavin, fat, fiber, protein, and other components of the corn grain;
2. It includes the discharge of polluting effluents (called nejayote), as the cost of treating nejayote before discarding it is too high to be done under the current scheme;
3. It is not suitable for instant flour production;
4. It involves long steeping times, with the attendant hygiene problems; and,
5. It uses subjective criteria to control the different stages of the process, resulting in a final product of varying quality.
Masa for tortilla can also be obtained by hydrating instant flour, which in turn is made from drying fresh masa. Although the quality of tortilla made from instant flour is inferior to that made from fresh masa, the industrial production of nixtamalized corn flour has become popular among the small and large tortilla producers because of its advantages insofar as distribution as storage are concerned.
Fresh masa for instant flour is manufactured by a variation of the traditional method. Smaller cooking time and temperature is used because the drying process causes additional gelatinization. The most commonly employed method is shown in U.S. Pat. No. 2,584,893, issued to W. R. Lloyd and R. Millares-Sotres, on February 1952. This patent uses pots with water, lime and corn. Water vapor is injected until boiling temperature is almost reached. The lime is kept in suspension by circulating the cooking water. To make tortillas, the mixture is kept at boiling temperature for 30 to 40 minutes; for other purposes such as snacks, this time is lower.
After cooking, cold water is added, and the corn is steeped for 1 to 6 hours. The nejayote is removed, the nixtamal is washed in rotating barrels with spraying water, and the grains are milled in a hammer mill. The resulting material is dried in a flash-type dryer and ground and sieved with a good control of the particle size distribution to obtain the required characteristics of the product.
However the disadvantages mentioned above are inherited to the current industrial method of flour production, in addition, the quality of tortillas made from instant flour is usually poorer than the quality of tortillas by the traditional method.
Prior efforts have been directed towards the improvement of the stability of the end products, the reduction of cooking time, the reduction of losses of a soluble alkali-substances, the improvement of the final product to approach that set by the traditional method.
For example, U.S. Pat. No. 2,704,257, issued to C.F.S. Diez de Sollano and J. M. Berriozabal on Mar. 15, 1955, discloses a method for producing corn tortilla flour which includes an improvement over the traditional nixtamalization process, by directly converting the wet nixtamal into a dry flour in one single milling and drying step. The traditional cooking and steeping steps, however, continue to be carried out prior to the milling and drying of the nixtamal corn grains.
U.S. Pat. No. 3,194,664, issued to Eytinge, B. D. on Jul. 13, 1965, discloses a method for the production of nixtamal, without departing from the traditional nixtamalization process continuous by providing a steeping receptacle at the top of which the corn kernels are continuously fed, and at the bottom of which an alkaline steeping solution is fed in counter-current with said kernels and at a suitable cooking temperature to accomplish the nixtamalization of the corn in a time of approximately 5 hours. Although this method represents an improvement over the traditional nixtamalization process, it requires the use of very costly equipment that is difficult to control.
U.S. Pat. No. 3,730,732, issued to Manuel Jesus Rubio, (May 1973), reports an increase in the yield of masa by incorporating water soluble alkaline substances. Also, Rubio reported that adding soluble alkaline substances to masa retards spoilage of tortillas. However, the tortillas tend to become hard and brittle.
U.S. Pat. No. 3,404,986, issued to Wimmer, et al, on Oct. 8, 1968, reported a method of manufacturing a corn flour with a rich whole corn flavor, different from flour obtained by lime treatment. These authors partially gelatinize a previously prepared corn meal with closely adjusted heated rotating rolls. The resulting flakes are thereafter ground to obtain corn flour. The instant flour obtained by this process can be used for fried snacks but not for the manufacture of tortillas.
Mexican patent No. 125,285, issued to Celorio on Apr. 25, 1972, describes a different process and apparatus for the preparation of nixtamalized corn flour by using a dry process in which a previously prepared corn meal with an appropriate amount of lime is heated in a chamber. The released moisture from the corn meal creates a humid and hot atmosphere within the nixtamalization chamber, sufficient for nixtamalization of the corn meal without the addition of an aqueous medium. This process, however, may be regarded as producing poor results in view of the fact that the admixture of the corn meal and the lime in a powdered state, leads to lack of inhomogenities in the nixtamalization process, with the consequent difficulties in quality control of the corn flour obtained by said process.
U.S. Pat. No. 4,513,018, issued to Rubio, M. J. on Apr. 23, 1985, discloses a continuous method for producing corn flour suitable for making tortillas, taco shells, tortilla chips and the like, which uses a modified nixtamalization process which includes the precooking of corn grains in the presence of lime within a vessel provided with a screw conveyor. The precooked kernels are then treated with a spray of hot water and are passed to a cooling zone where they remain for a time sufficient to reabsorb a sufficient amount of water. The steeped grains are milled and the flour is classified and re-milled until the desired particle size is obtained. In this way cooking is done continuously, which represents an improvement over the traditional nixtamalization process, although the main problem of the traditional method remains.
U.S. Pat. No. 4,594,260, issued to M. C. Vaqueiro and P. Reyes on Jun. 10, 1986, discloses a method for obtaining corn flour, in which the hull is removed from the germ and endosperm of the corn kernel. The hull is nixtamalized by the traditional method and then re-mixed with the non-nixtamalized endosperm and germ fractions. This method, although more efficient than the traditional method in view of the fact that only a small fraction of the corn kernel has to be nixtamalized, requires rather elaborate equipment to separate the hull fraction. Also the hull must be free of endosperm fractions in order to produce a good quality of masa for instant flour preparation.
Other methods of instant flour production have been proposed. Montemayor and Rubio in the paper xe2x80x9cAlkaline cooked corn flour: Technology and uses in tortilla and snack products. (abstr.) Cereal Foods World 28:577, 1983xe2x80x9d described continuous and discontinuous (batch) processes in which the lime, water, and corn mixture are placed in a spiral band in a vapor atmosphere, in such a way that the corn is cooked as it is transported. The corn is later washed to remove part of the pericarp and excess lime, dried, and ground.
Molina, M. R., Letona, M., and Bressani, R., 1977 (Drum drying technology for the improved production of instant tortilla flour. J. Food Sci. 42:1432-1434), reported the use of a double drum dryer with an internal pressure of 1.1-1.83 kg/cm2 (15-26 psi) and a temperature of 93-104xc2x0 C. These dryers give lower losses of solids, but their energy consumption is high.
Mendoza (1975) reported a method using a vapor chamber with a temperature in the 80-120xc2x0 C. range.
Sterner and Zone (1981) used the heat generated during grinding of the waterlime-corn mixture to cook the corn. Some of these processes grind the whole corn grain and the starch granules are exposed to over-gelatinization or low hydrolysis of the pericarp, resulting in a masa of poor quality.
On the other hand, some industrial producers of tortilla use fresh masa to make tortilla because the quality of the texture and flavor of tortilla made from instant corn flour is lower than that made from fresh masa, and the drying process is energetically expensive (Gomez, M. H., Rooney, L. W., Waniska, R. D. and Pflugfelder, R. L. 1987; Dry corn masa flours for tortilla and snack production; Cereal Foods World. 32:372).
Unfortunately, none of these methods provide an integral solution to the tortilla industry. They either it solve all problems to an adequate level but use a complicated and expensive process, or they retain the drawback of the traditional process. Our method is simple and inexpensive and addresses all the problems of tortilla production.
A main objective of the present invention is to provide a system and a process for the production of fresh whole corn masa, instant corn flour and derived products using high pressure, with out producing polluting effluents.
Another objective of the present invention is to provide a system and a process for the production of fresh whole corn masa, instant corn flour and derived products, using high pressure, which uses the whole corn grain, avoiding the loss of vitamins, minerals, protein, fat, and fiber of the germ and pericarp, that are lost during the traditional and industrial processes.
Another objective of the present invention is to provide a system and a process for the production of fresh whole corn masa, instant corn flour and derived products, using high pressure, wherein the processing time is short.
An additional objective of the present invention is to provide a system and a process for the production of fresh whole corn masa, instant corn flour and derived products, wherein pericarp hydrolysis and water absorption are achieved in a short time by high temperatures and high pressures, using a small amount of lime.
Another objective of the present invention is to provide a system and a process for the production of fresh whole corn masa, instant corn flour and derived products, wherein all the solubilized nutrients are not wasted and, in fact, contribute to improve the the rheological characteristics of tortilla produced from this masa.
An additional objective of the present invention is to provide a system and a process for the production of fresh whole corn masa, instant corn flour and derived products, wherein the whole masa can be used for the production of tortillas and corn chips or, through the stages of dehydration, milling and sieving for the production of nixtamalized whole corn instant flour.
These and other objectives and additional advantages of the present invention will become evident to the experts in the field from the following detailed description of the invention, and a specific embodiment of the same will also be described in an illustrative sense without, however, limiting this invention.